Is it possible to execute a .NET dll without an exe to load it?

Question

I\'m curious if there\'s a way to execute a static .DLL method in a new process without having to create an .EXE for it?

AFAIK, this isn\'t possible with native Win3

Answer 1

Look into the the rundll32.exe program that ships with windows. If you know certain information about the dll, you can sometimes use this program to run code in that dll.

Answer 2

A .NET Assembly can be loaded in PowerShell. (Well, PowerShell is an EXE, but not specialized for running code from any particular assembly)

Answer 3

Option 1: .NET InstallUtil (part of the normal .NET install)

Add a reference to System.Configuration.Install then drop something like this in your assembly:

[System.ComponentModel.RunInstaller(true)]
public class Sample : System.Configuration.Install.Installer
{
    public override void Uninstall(System.Collections.IDictionary savedState)
    {
        base.Uninstall(savedState);

        this.Context.LogMessage("This can be in a .dll.");
        // Do your thing...
    }
}

Then abuse the .NET InstallUtil:

%windir%\Microsoft.NET\Framework\v2.0.50727\installutil /logtoconsole=false /logfile= /u [your assembly .dll here]

It may be a bit messy, especially without all the command line parameters disabling logging.

Option 2: use native rundll32 to inverse P/Invoke a static class method

2016 Edit: Now a Nuget package: UnmanagedExports (src)!

Unknown MSIL directives (msdn forum, 2007) links to a beta 1 release of the IL Assembly Language Programmer's Reference (10/3/2000, pg.74) which states:

If fromunmanaged is specified, the runtime will automatically generate a thunk that will convert the unmanaged method call to a managed call, call the method, and return the result to the unmanaged environment.

There is more detail in Expert .NET 2.0 IL assembler and Inside Microsoft. NET IL Assembler. (Best search keywords: ilasm vtentry).

Related reading:

Unmanaged Exports: Cannot compile assembly (stackoverflow, 2010)

Unmanaged Exports / RGiesecke.DllExport.dll (stackoverflow, 2010)

Create a C# DLL That Can Be Imported in a Delphi App Using stdcall (stackoverflow, 2009)

C# Project Template for Unmanaged Exports (Robert Giesecke, 2010) - msbuild, vs2010 integration

IKVM.Reflection Update: export static managed methods as unmanaged DLL exports (mono, 2011)

Simple Method of DLL Export without C++/CLI (codeproject, 2009) - no 64-bit support?

How to Automate Exporting .NET Function to Unmanaged Programs (codeproject, 2006) - supports 64-bit

Has anything been added to .Net 4.0 to support "Reverse P/Invoke" scenarios? (msdn forum, 2010) - code listing

Unmanaged code can wrap managed methods (codeproject, 2004)

Potential drawbacks:

Gotchas with Reverse Pinvoke (unmanaged to managed code callbacks) (msdn blog, 2006)

Reverse P/Invoke and exception (msdn blog, 2008)

Answer 4

You can launch a process and run a dll function by using rundll32.exe dll_name,method_name. In C# you can do something like this:

myProcess = new Process {StartInfo = {FileName = "rundll32.exe", Arguments = "my_dll_name.dll,my_function_name"}};
myProcess.Start();

Just make sure the DLL is in your PATH. If you are thinking about running unit testing of some kind, make sure you kill the process on the TearDown / CleanUp method: myProcess.Kill(), otherwise the DLL may remain loaded and you won't be able to overwrite it as part of your development process. You should also look into this article for a command line application that will kill all processes holding your DLL and add it to your Pre-Build events: freelib.exe my_dll_name.dll

Answer 5

Just start a PowerShell prompt.

  [Reflection.Assembly]::LoadFile("Name of your dll")
  [Your.NameSpace.And.TypeName]::YourMethod()

I see you want this from C#

Create the Type using the Assembly Qualified name:

 var t = Type.GetType("NameSpace.Type,Name Of Dll");
 var m = t.GetMethod("NameOfMethod");
 m.Invoke(null, new object[] { params });

This should get you started.

I don't exactly know what you mean by "In a new process", but it should not be to difficult to wrap this into a .exe/.ps1 that you can start with some option on the commandline.

So you do not have to create a new .exe for every DLL you want to invoke.

But if you want to start a new process, you should start a new process, this is typically done by starting a new .EXE.